feat(domain): add DomainError::UniqueViolation {field}

crates/domain/src/errors.rs

@@ -10,6 +10,8 @@ pub enum DomainError {
     Forbidden,
     #[error("conflict: {0}")]
     Conflict(String),
+    #[error("unique violation on field: {field}")]
+    UniqueViolation { field: &'static str },
     #[error("invalid input: {0}")]
     InvalidInput(String),
     #[error("external service error: {0}")]

crates/presentation/src/errors.rs

@@ -27,6 +27,9 @@ impl IntoResponse for ApiError {
             }
             Self::Domain(DomainError::Forbidden) => (StatusCode::FORBIDDEN, "forbidden".into()),
             Self::Domain(DomainError::Conflict(m)) => (StatusCode::CONFLICT, m),
+            Self::Domain(DomainError::UniqueViolation { field }) => {
+                (StatusCode::CONFLICT, format!("{field} already taken"))
+            }
             Self::Domain(DomainError::InvalidInput(m)) => (StatusCode::UNPROCESSABLE_ENTITY, m),
             Self::Domain(DomainError::ExternalService(_)) => {
                 (StatusCode::BAD_GATEWAY, "external service error".into())